Kamal Hamami, a member of the Free Syrian Army's SupremeMilitary Council, known by his nom de guerre Abu Basselal-Ladkani, was meeting with members of the Islamic State ofIraq and the Levant in the port city of Latakia when they killedhim, Qassem Saadeddine, a Free Syrian Army spokesman, toldReuters.

"The Islamic State phoned me saying that they killed AbuBassel and that they will kill all of the Supreme MilitaryCouncil," Saadeddine said from Syria.

"He met them to discuss battle plans," Saadeddine added.

The Free Syrian Army has been trying to build a network oflogistics and reinforce its presence across Syria as the U.S.administration pledged to send weapons to the group after itconcluded that Syrian President Bashar al-Assad's forces hadused chemical weapons against rebel fighters.

U.S. congressional committees are holding up the planbecause of fears that such deliveries will not be decisive andthe arms might end up in the hands of Islamist militants,security sources have said.

While Free Syrian Army units sometimes fight alongsideIslamist militant groups such as the Islamist State, rivalrieshave increased and al Qaeda-linked groups have been blamed forseveral assassinations of commanders of moderate rebel units.